for suburban trains as far as Erkner. Deutsche Reichsbahn and World War II The Prussian railways, including the Lower Silesian-Mark railway became part of Deutsche Reichsbahn on its founding in 1920. The suburban line to Erkner was electrified in 1928 using a lateral-contact third-rail system. This and other Berlin lines were subsequently rebranded as the Berlin S-Bahn, while the long-distance services were still operated by steam. After World War II The Frankfurt (Oder)–Poznań line, which branches off the Lower Silesian-Mark line at Frankfurt (Oder) is part of an east–west link via Warsaw to Moscow. As Soviet troops advanced this line was rebuilt with () for the supply of the Red Army, so that on 25 April 1945 the first Soviet military train could reach the Berlin city limits. On 28 June 1945, the first passenger train ran from Moscow to the Silesian station. In order for Joseph Stalin to travel to the Potsdam Conference a track to Potsdam was also changed to Russian broad gauge. The broad gauge tracks were returned to standard gauge by 20 September 1945 in order to increase rail capacity. Unlike most of the lines in the Soviet zone the mainline between Berlin and Frankfurt (Oder) did not have one of its two tracks removed to provide reparations for the USSR as it was required for the transport of the reparations. In the 1980s the German Democratic Republic electrified the line to Oderbrücke station on the 15 kV 16.7 Hz AC system and the line is today a major axis of international traffic again. The Guben–Zagan (Sagan) section of the Lower Silesian-Markish line runs over the Oder-Neisse line, the post-war boundary between Germany and Poland. Passenger services were closed and not resumed until 1972, but were then closed again in 1981 because of political developments in Poland. In 1996, Polish State Railways began operating three pairs of passenger trains between Gubinek and Guben again. Patronage was very low, so that on 6 October 2002 services were terminated. Freight traffic was mainly channelled through other routes, and the last freight train to use the route ran in 1994. Current situation Today, Deutsche Bahn operates Regional-Express line RE1 (Magdeburg–Berlin–Frankfurt (Oder)–Eisenhüttenstadt) and RE11 (Frankfurt (Oder)–Eisenhüttenstadt–Guben–Cottbus) on the line. In Berlin section the S3 S-Bahn service runs parallel with the mainline. Since 2002, the Berlin-Frankfurt (Oder) line has been upgraded for speeds of up to 160 km/h, at a cost